Feature request: Add functionality to preload image using SDWebImage

[otusweb]

The current SDK allows to load an image straight to an UIImageView. In my case i'd like to preload the image before setting in the imageView as I have to calculate some layout that requires having the image locally.

here is a swift version of the method I created to do just that:

class func imageForReference(_ reference: StorageReference, completion: @escaping (UIImage?, Error?) -> Void) {
        // Query cache for image before trying to download
        let cache = SDImageCache.shared()
        let key = reference.fullPath
        var cached = cache.imageFromMemoryCache(forKey: key)
        if cached != nil {
            completion(cached, nil)
            return
        }

        cached = cache.imageFromDiskCache(forKey: key)
        if cached != nil {
            completion(cached, nil)

            return
        }

        // If nothing was found in cache, download the image from Firebase Storage
        let filePath = FileManager.default.temporaryDirectory.appendingPathComponent(key)
        reference.write(toFile: filePath) { (file: URL?, error: Error?) in
            DispatchQueue.main.async {
                guard error == nil, let file = file else {
                    completion(nil, error)
                    return
                }
                let image = UIImage(contentsOfFile: file.absoluteString)
                cache.store(image, forKey: key, completion: nil)

                completion(image, nil)
            }
        }
    }

[dreampiggy]

@otusweb See #654 . I've create PR to use the SDWebImage 5.0 for better integration.

When using the Custom Loader API of SDWebImage 5.0, you can share the same logic for all built-in methods from SD.

For example, you can even use SDWebImagePrefetcher to prefetch FIRStorageRef instance. Show the demo code:

// Setup code. If you using the global `loadersManager`, to bind multiple loaders like (downloader, firebaseloader), you don't need this code.
let manager = SDWebImageManager(cache: SDImageCache.shared, loader: SDWebImageFIRStorageLoader.shared)
let prefetcher = SDWebImagePrefetcher(manager: manager)

// Now let's prefetch
let references: [StorageReference]
let urls = references.compactMap { URL.sd_URL(with: $0) }
prefetcher.prefetch(urls: urls)

// Done :)

[morganchen12]

654 has been merged and released.

[Spiderpowa]

In case anyone found this issue, SDWebImageFIRStorageLoader is now StorageImageLoader in the example code.

@otusweb See #654 . I've create PR to use the SDWebImage 5.0 for better integration.

When using the Custom Loader API of SDWebImage 5.0, you can share the same logic for all built-in methods from SD.

For example, you can even use SDWebImagePrefetcher to prefetch FIRStorageRef instance. Show the demo code:

// Setup code. If you using the global `loadersManager`, to bind multiple loaders like (downloader, firebaseloader), you don't need this code.
let manager = SDWebImageManager(cache: SDImageCache.shared, loader: SDWebImageFIRStorageLoader.shared)
let prefetcher = SDWebImagePrefetcher(manager: manager)

// Now let's prefetch
let references: [StorageReference]
let urls = references.compactMap { URL.sd_URL(with: $0) }
prefetcher.prefetch(urls: urls)

// Done :)